但是有没有一个词专门指手臂弯曲处内侧，也就是手肘内侧的褶皱处呢？

Is there a name for the inside of the arm bend; the crease inside your elbow?

youdao

这一现象是指光线在时空中传播的过程中由于大质量物质的引力而发生弯曲，这也是爱因斯坦的广义相对论所预言的。

This phenomenon, predicted by Einstein's theory of general relativity, causes light to curve as it flies through space-time that has been dented by the gravity of large bodies of mass.

youdao

(航空学)指飞艇或者飞船，其外形由坚固、不可弯曲的构架或者结构所支撑。

(aeronautics) designating an airship or dirigible having a form maintained by a stiff unyielding frame or structure.

youdao